What is MQTT?
MQTT stands for Message Queuing Telemetry Transport. It is a lightweight communication protocol designed for fast, efficient and reliable data transfer between devices over networks with limited bandwidth or high Latency.
MQTT is widely used in Industrial Internet of Things (IIoT), SCADA systems, sensor networks and Cloud integrations.
📡 Characteristics of MQTT
- Publish/subscribe (pub/sub) model:
- Devices publish messages to a “topic”
- Other devices subscribe to those topics to receive data
- Lightweight: little overhead, ideal for Embedded systems or field devices
- Runs on top of TCP/IP
- Supports Quality of Service (QoS) levels for reliable delivery
- Often used with TLS for encryption and security
🏭 Applications in OT and IIoT
| Application | Example |
|---|---|
| Sensor communication | Temperature or vibration sensor sends data to the Cloud |
| Cloud integration | A PLC publishes process data to MES or Cloud |
| Remote Monitoring | A SCADA system receives MQTT messages from edge devices |
| Maintenance and analytics | Devices send status, faults or maintenance data |
🔄 MQTT architecture
- Client: any device (e.g. Sensor, gateway, SCADA) that sends or receives messages
- Broker: central server that receives and forwards messages to subscribed clients
- Well-known brokers: Mosquitto, HiveMQ, EMQX
📎 MQTT is event-driven and scalable: new clients can join easily.
🔐 Security
- TLS for encryption of messages
- Authentication via username/password or certificates
- Firewall, VLAN and the zone-and-conduits model for network protection
- Defense in Depth is essential when using MQTT in OT networks
📌 In summary
MQTT is a lightweight and efficient protocol for real-time data communication, ideal for industrial environments with many Sensors, edge devices and cloud integrations. Thanks to its simple structure and flexibility, it is a key element of modern IIoT architectures.